In recent years, a transparent screen has been proposed that has transparency to transmit background light and causes image light projected from a projector to undergo diffused reflection or diffused transmission to display an image. When this transparent screen is used, for example, it is possible to display a projected image superimposed on a night view in a window of a skyscraper, and to display a projected image superimposed on products in an exhibition window of a store. In this way, the transparent screen is expected as a key device for implementing new image representation by a projector.
As a transparent screen of a transmission type, a transparent screen of a transmission type including special diffusion microparticles has been proposed (for example, refer to PTL 1). These diffusion microparticles are distributed in a very small amount within the transparent screen of a transmission type. This transparent screen of a transmission type diffuses part of image light greatly and displays an image, and transmits background light rectilinearly.
Part of the diffused light is reflected by an interface between a back surface of the transparent screen and the air. Therefore, the transparent screen of a transmission type having the above-described configuration can be used as a transparent screen of a reflection type.
Furthermore, as the transparent screen of a reflection type, the following transparent screen of a reflection type has been proposed. One example of the transparent screen of a reflection type includes a plurality of protrusions, a selective reflection layer provided in the plurality of protrusions, and a transparent material covering a front surface of the selective reflection layer. The selective reflection layer selectively reflects right-handed circularly polarized or left-handed circularly polarized laser light having a wavelength of a characteristic (refer to PTL 2). Another example of the transparent screen of a reflection type has a light-reflecting region partially provided in a transparent base material (refer to PTL 3).
An observer can enjoy an image while observing background by using such a transparent screen of a transmission type or reflection type.